Epoxy resins have been employed in a variety of fields because of their excellent properties such as heat resistance, adhesion, water resistance, mechanical strength and electrical properties. Especially in electrical and electronic fields, epoxy resins have found widespread use as electrical insulation castings, laminating materials and materials for encapsulation. However, in recent years, with the miniaturization, high precision and high performance of electrical and electronic components, there has been a demand for molding properties, high moisture resistance and high electrical properties of epoxy resins to be used.
For example, recently, LSI packaging is showing the trend of high density and thin shape, with the development of portable devices such as IC cards, LCDs, portable telephones and note-type personal computers, and is changing the process thereof from the conventional transfer-molding packaging to so-called COB (chip-on-board) or TAB processes in which bare chips are mounted and are encapsulated with liquid encapsulating materials. The epoxy resins that are made from bisphenol A or bisphenol F are main streams of the conventional epoxy resins for liquid encapsulation. However, there has been a demand for the improvement of reliability of liquid encapsulating materials because these resins have poor moisture resistance and poor heat resistance.
A method has been proposed in which biphenyl type crystalline epoxy resins having low stress, low moisture absorption, and excellent crack-resistance in soldering, which are used in large quantities as LSI-packaging materials for transfer molding use, or to make the resins have a low melting point, is liquefied or subjected to have a low melting point (confer Japanese Unexamined Patent Publication No. Sho 07-62060). However, in this method, since considerably large amounts of phenol compounds or compounds having carboxyl groups are subjected to a reaction with biphenyl type epoxy resins, obtained epoxy resins do not have satisfactory curing characteristics and cured resins therefrom do not have satisfactory heat resistance.